Elon Musk, the billionaire founder and CEO of the private spaceflight company SpaceX, wants to help establish a Mars colony of up to 80,000 people by ferrying explorers to the Red Planet for perhaps $500,000 a trip.
(...) we've put all our eggs in one basket. If we were on many worlds and were to mess up down here, there's a way for the human species to continue. I don't for a moment propose that the Earth is a disposable planet, and we have to put enormous efforts into making sure we don't muss up down here. But there is a chance.
FWIW, while researching my Moore's law essay, I found materials claiming that underground construction was more expensive but paid for itself via better heating/cooling. But that was for shallow cut-and-scrape constructions and I suspect 1 meter wouldn't take care of supernova radiation.
As far as I understand the issue, the danger is mainly from the temporary ozone layer depletion, with the resulting solar UV rays doing most of the damage, and not from any kind of direct supernova radiation. And UV is not hard to shield from.